U.S. patent application number 16/845211 was filed with the patent office on 2020-10-15 for electrically powered suspension system.
The applicant listed for this patent is HONDA MOTOR CO., LTD.. Invention is credited to Satoshi OHNO, Atsuhiko YONEDA.
Application Number | 20200324604 16/845211 |
Document ID | / |
Family ID | 1000004764344 |
Filed Date | 2020-10-15 |
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United States Patent
Application |
20200324604 |
Kind Code |
A1 |
OHNO; Satoshi ; et
al. |
October 15, 2020 |
ELECTRICALLY POWERED SUSPENSION SYSTEM
Abstract
An electrically powered suspension system 11 achieves vibration
control of a vehicle without disturbing a vehicle behavior and
impairing riding comfort even if an electric motor 31 of an
electromagnetic actuator 13 generates excessive heat, wherein the
electromagnetic actuator 13 includes the electric motor 31
generating a driving force for vibration damping and
extension/contraction; a target damping force setting part 51
setting a target damping force; a target extension/contraction
setting part 53 setting a target extension/contraction force; and a
drive controller 49 performing the drive control of the electric
motor 31 using a drive force based on the target damping force and
target extension/contraction force by limiting the motor current
not to exceed a current threshold that is an addition of a damping
current threshold and extension/contraction current threshold,
which thresholds are separately configured considering a priority
of riding comfort and steering stability.
Inventors: |
OHNO; Satoshi; (Wako-shi,
JP) ; YONEDA; Atsuhiko; (Wako-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HONDA MOTOR CO., LTD. |
Tokyo |
|
JP |
|
|
Family ID: |
1000004764344 |
Appl. No.: |
16/845211 |
Filed: |
April 10, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60G 2400/71 20130101;
B60G 2400/90 20130101; B60G 2400/252 20130101; B60G 17/0157
20130101; B60G 2202/42 20130101 |
International
Class: |
B60G 17/015 20060101
B60G017/015 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 12, 2019 |
JP |
2019-076547 |
Claims
1. An electrically powered suspension system comprising: an
electromagnetic actuator including an electric motor generating a
driving force used for vibration damping and extension/contraction;
a target current calculator calculating respectively a target
damping current for generating a target driving force used for the
vibration damping and a target extension/contraction current for
generating a target driving force used for the
extension/contraction; and a drive control unit performing a drive
control of the electric motor using a drive current based on the
target damping current and the target extension/contraction
current, wherein the drive control unit performs the drive control
of the electric motor using the drive current for the electric
motor, the drive current being limited so as not to exceed a
preconfigured current limitation threshold; the current limitation
threshold includes an damping current limitation threshold for the
target damping current and an extension/contraction current
limitation threshold for the target extension/contraction current;
and the damping current limitation threshold and the
extension/contraction current limitation threshold are configured
separately from each other.
2. The electrically powered suspension system according to claim 1,
wherein the extension/contraction current limitation threshold is
set to a value smaller than the damping current limitation
threshold.
3. The electrically powered suspension system according to claim 1,
wherein the damping current limitation threshold and the
extension/contraction current limitation threshold each is
determined on a basis of a current correlation value correlating
with the drive current of the electric motor.
4. The electrically powered suspension system according to claim 1,
further comprising an information acquisition part that acquires
information on a temperature of the drive control unit, wherein the
damping current limitation threshold and the extension/contraction
current limitation threshold each is determined on a basis of the
temperature of the drive control unit.
5. The electrically powered suspension system according to claim 1,
further comprising an information acquisition part that acquires
information on a temperature of the electric motor, wherein the
damping current limitation threshold and the extension/contraction
current limitation threshold each is configured on a basis of the
temperature of the electric motor.
6. The electrically powered suspension system according to claim 1,
wherein the damping current limitation threshold and the
extension/contraction current limitation threshold each is
separately configured in consideration of at least a priority on
riding comfort and driving stability of the vehicle.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of foreign priority to
Japanese Patent Application No. 2019-076547, filed on Apr. 12,
2019, which is incorporated by reference in its entirety.
TECHNICAL FIELD
[0002] The present invention relates to an electrically powered
suspension system including an electromagnetic actuator. The
electromagnetic actuator is disposed between a vehicle body and a
wheel and includes an electric motor that generates a driving force
used for vibration damping and extension/contraction.
BACKGROUND ART
[0003] A conventionally well-known electrically powered suspension
system includes an electromagnetic actuator that is installed
between a vehicle body and a wheel, and includes an electric motor
generating a driving force used for vibration damping and
extension/contraction (for example, see PTL 1). The electromagnetic
actuator includes a ball screw mechanism in addition to the
electric motor. The electromagnetic actuator operates to generate a
driving force for the vibration damping and extension/contraction
by converting rotary motion of the electric motor into linear
motion of the ball screw mechanism.
[0004] Here, the driving force used for the vibration damping is
called as a damping force. The damping force means a force directed
to a different direction from a direction of a stroke speed of the
electromagnetic actuator. On the other hand, the driving force used
for the extension/contraction is called as an extension/contraction
force. The extension/contraction force means a force generated
regardless of the direction of the stroke speed.
[0005] In addition, another technique is known, to protect a motor
mounted on the vehicle from damage by constantly monitoring a
temperature of the motor and determining the motor current is in an
excessive heat generation state and then limiting the motor current
if the temperature of the motor exceeds a predetermined temperature
(for example, see PTL 2).
CITATION LIST
Patent Literature
[0006] PTL 1: Japanese Patent Application Unexamined Publication
No. 2010-132222
[0007] PTL 2: Japanese Patent Application Unexamined Publication
No. 2003-019973
SUMMARY OF INVENTION
Technical Problem
[0008] Here, it is assumed that the electrically powered suspension
system according to PTL 1 is provided with a motor protection
technology according to PTL 2, to perform damping control of an
electromagnetic actuator having an electric motor as a driving
force source. In such a motor protection technology, the electric
motor is assumed to be in an excessive heat generation state. And,
a value of a drive current supplied to the electric motor is
uniformly limited with a predetermined limitation threshold in
order to protect the electric motor from damage.
[0009] In such a case of the excessive heat generation state, the
damping force generated by the electromagnetic actuator becomes
weaker than in a normal state. Then, the unsprung vibration becomes
not sufficiently suppressed. As a result, the behavior of the
vehicle may be disturbed.
[0010] Similarly, the extension/contraction force of the
electromagnetic actuator is weakened in the excessive heat
generation state as compared with the normal state. Then, for
example, the vehicle may not be kept in a stable posture based on a
skyhook control. This result in a possibility that riding comfort
of the vehicle may be impaired.
[0011] The present invention is made in view of the above problems,
and an object of the present invention is to provide an
electrically powered suspension system capable of performing
vibration control of a vehicle without disturbing a behavior of the
vehicle and without impairing the riding comfort of the vehicle as
much as possible even when the electric motor provided in the
electromagnetic actuator is in an excessive heat generation
state.
Solution to Problem
[0012] In order to achieve the above object, the present invention
provides an electrically powered suspension system comprising: an
electromagnetic actuator disposed between a vehicle body and a
wheel and including an electric motor generating a driving force
used for vibration damping and for extension/contraction; a damping
force calculator calculating a target damping force that is a
target value of the vibration damping used for the electromagnetic
actuator; an extension/contraction force calculator calculating a
target extension/contraction force that is a target value of the
extension/contraction of the electromagnetic actuator; a drive
controller that performs drive control of the electric motor using
a target driving force based on the damping force calculated by the
damping force calculator and the target extension/contraction force
calculated by the extension/contraction force calculator, wherein
the drive controller performs a drive control to limit a drive
current for the electric motor so that a current correlation value
correlated with the drive current for the electric motor does not
exceed a predetermined current limitation threshold; and the
current limitation threshold includes a damping current limitation
threshold for acquiring a target driving force based on the target
damping force and an extension/contraction current limitation
threshold for acquiring a target driving force based on the target
extension/contraction force; and the damping current limitation
threshold and the extension/contraction current limitation
threshold may be set separately.
Advantageous Effects of Invention
[0013] The present invention allows an electrically powered
suspension system to perform vibration control of a vehicle without
disturbing a behavior of the vehicle and without impairing riding
comfort of the vehicle as much as possible even when the electric
motor provided in the electromagnetic actuator is in an excessive
heat generation state.
BRIEF DESCRIPTION OF DRAWINGS
[0014] The drawings described herein are for illustration purposes
only and are not intended to limit the scope of the present
disclosure in any way.
[0015] FIG. 1 is an overall configuration diagram of an
electrically powered suspension system according to an embodiment
of the present invention.
[0016] FIG. 2 is a partial sectional view of an electromagnetic
actuator provided in the electrically powered suspension
system.
[0017] FIG. 3 is a block diagram of internal and peripheral
portions of an ECU (Electronic Control Unit) included in the
electrically powered suspension system.
[0018] FIG. 4A is a block diagram conceptually showing an internal
configuration of an example of a driving force calculator included
in the ECU provided in the electrically powered suspension
system.
[0019] FIG. 4B is an explanatory diagram conceptually illustrating
a target damping force map describing a relationship between a
target damping force and a stroke speed in which the target damping
force varies in response to changes of the stroke speed.
[0020] FIG. 4C is an explanatory diagram conceptually illustrating
a target extension/contraction force map describing a relationship
between a target extension/contraction force and a sprung speed in
which the target extension/contraction force varies in response to
changes of the sprung speed.
[0021] FIG. 5A is an explanatory diagram conceptually illustrating
a pre/post-limitation target value map according to the embodiment,
which map describes a relationship between before and after the
target damping force and the target extension/contraction force are
limited when a control current limitation command signal is
received.
[0022] FIG. 5B is an explanatory diagram conceptually illustrating
a pre/post-limitation target value map according to a modification,
which map describes a relationship between before and after the
target damping force and the target extension/contraction force are
limited when the control current limitation command signal is
received.
[0023] FIG. 6 is a flowchart describing an operation of the
electrically powered suspension system according to the embodiment
of the present invention.
[0024] FIG. 7A is a block diagram conceptually showing an internal
configuration of a first modification of the driving force
calculator included in the ECU of the electrically powered
suspension system.
[0025] FIG. 7B is a block diagram conceptually showing an internal
configuration of a second modification of the driving force
calculator included in the ECU of the electrically powered
suspension system.
DESCRIPTION OF EMBODIMENTS
[0026] Hereinbelow, description is given of an electrically powered
suspension system according to an embodiment of the present
invention in detail with reference to the drawings as
appropriate.
[0027] In the drawings described below, members having functions
common thereto are denoted by common reference numerals. Further, a
size and shape of the member may be schematically represented by
deformation or exaggeration for convenience of explanation.
Basic Configuration Common to All Embodiments of the Present
Invention
[0028] First, description is given of a basic configuration common
to all the electrically powered suspension systems 11 according to
embodiments of the present invention with reference to FIGS. 1 and
2.
[0029] FIG. 1 is a diagram showing the overall configuration of an
electrically powered suspension system 11 according to one
embodiment of the present invention. FIG. 2 is a partially
sectional view of an electromagnetic actuator 13 partially
constituting the electrically powered suspension system 11.
[0030] As shown in FIG. 1, the electrically powered suspension
system 11 according to the embodiment of the present invention
includes a plurality of electromagnetic actuators 13 provided for
respective wheels 10 and one electronic control device
(hereinbelow, referred to as "ECU") 15. The ECU 15 is connected
with each of the plurality of the electromagnetic actuators 13
through a power supply line 14 (see a solid line in FIG. 1)
supplying drive control power from the ECU 15 to each
electromagnetic actuators 13 and a signal line 16 (see a broken
line in FIG. 1) transmitting a rotation angle signal of the
electric motor 31 (see FIG. 2).
[0031] In the present embodiment, four of the electromagnetic
actuators 13 are provided respectively to the wheels including
front wheels (front right wheel, front left wheel) and rear wheels
(rear right wheel, rear left wheel). The electromagnetic actuators
13 provided for each wheel are driven and controlled separately
from each other in each synchronization with the
extension/contraction for each wheel.
[0032] In the embodiment of the present invention, unless otherwise
stated, each of the plurality of electromagnetic actuators 13 has a
configuration common to each other. Therefore, all the plurality of
electromagnetic actuators 13 are described by explaining a
configuration of one electromagnetic actuator 13.
[0033] As shown in FIG. 2, the electromagnetic actuator 13 includes
a base housing 17, an outer tube 19, a ball bearing 21, a ball
screw shaft 23, a plurality of balls 25, a nut 27, and an inner
tube 29.
[0034] The base housing 17 rotatably supports a base end portion of
the ball screw shaft 23 around it with interposition of the ball
bearing 21. The outer tube 19 is provided on the base housing 17
and accommodates a ball screw mechanism 18 including the ball screw
shaft 23, the plurality of balls 25, and the nut 27. The plurality
of balls 25 roll along a screw groove of the ball screw shaft 23.
The nut 27 is engaged with the ball screw shaft 23 with
interposition of the plurality of balls 25, and converts rotational
motion of the ball screw shaft 23 into linear motion. The inner
tube 29 connected to the nut 27 is integrated with the nut 27 and
displaceable in an axial direction of the outer tube 19.
[0035] As seen in FIG. 2, the electromagnetic actuator 13 includes
the electric motor 31, a pair of pulleys 33, and a belt member 35
in order to transmit a rotational driving force to the ball screw
shaft 23. The electric motor 31 is provided on the base housing 17
so as to be arranged in parallel with the outer tube 19. The
pulleys 33 are respectively attached to a motor shaft 31a of the
electric motor 31 and the ball screw shaft 23. The belt member 35
for transmitting the rotational driving force of the electric motor
31 to the ball screw shaft 23 is put round the pair of pulleys
33.
[0036] The electric motor 31 is provided with a resolver 37 for
detecting a rotation angle of the electric motor 31. The rotation
angle of the electric motor 31 detected by the resolver 37 is sent
to the ECU 15 via the signal line 16. The electric motor 31 is
controlled in its rotational driving force by the ECU 15 in
accordance with the drive control power to be supplied to each of
the plurality of electromagnetic actuators 13 via the power supply
line 14.
[0037] According to this embodiment, as seen in FIG. 2, a dimension
in the axial direction of the electromagnetic actuator 13 is
shortened by employing a layout in which the motor shaft 31a of the
electric motor 31 and the ball screw shaft 23 are arranged
substantially in parallel and connected with each other. However,
another layout may be employed in which, for example, the motor
shaft 31a of the electric motor 31 and the ball screw shaft 23 are
coaxially arranged and connected to each other.
[0038] As seen in FIG. 2, the electromagnetic actuator 13 according
to this embodiment has a connecting portion 39 provided at a lower
end of the base housing 17. The connecting portion 39 is connected
and fixed to an unsprung member (not shown) such as a lower arm and
a knuckle provided on the wheel. On the other hand, an upper end
portion 29a of the inner tube 29 is connected and fixed to a sprung
member (not shown) such as a strut tower portion provided on the
vehicle body. In other words, the electromagnetic actuator 13 is
arranged in parallel with a spring member (not shown) provided
between the body and the wheel of the vehicle 10. The sprung member
is provided with a sprung acceleration sensor 40 (see FIG. 3)
detecting the acceleration of the vehicle body (sprung) along the
stroke direction of the electromagnetic actuator 13.
[0039] The electromagnetic actuator 13 configured as described
above operates as follows. For example, it is assumed that momentum
relating to upward vibration is inputted to the connecting portion
39 from a wheel of the vehicle 10. In this case, the inner tube 29
and the nut 27 are about to together descend with respect to the
outer tube 19 to which the momentum relating to the upward
vibration has been applied. In response to the above momentum, the
ball screw shaft 23 tries to rotate in a direction following the
descending of the nut 27. At this time, the rotational driving
force of the electric motor 31 is generated in a direction
preventing the nut 27 from descending. The rotational driving force
of the electric motor 31 is transmitted to the ball screw shaft 23
via the belt member 35.
[0040] In this way, the vibration transmitted from the wheel to the
vehicle body is damped by applying a reaction force (damping force)
that is against the momentum relating to the upward vibration to
the ball screw shaft 23.
<Configuration of Internal and Peripheral Parts of ECU
15>
[0041] Next, an internal configuration and a peripheral
configuration of the ECU 15 equipped in the electrically powered
suspension system 11 is described with reference to FIGS. 3, 4A,
4B, 5A, and 5B.
[0042] FIG. 3 is a diagram showing the internal configuration and
peripheral configurations of the ECU 15 equipped in the
electrically powered suspension system 11. FIG. 4A is a diagram
conceptually illustrating an internal configuration of a driving
force calculator 47A according to the embodiment provided in the
ECU 15 of the electrically powered suspension system 11. FIG. 4B is
an explanatory diagram conceptually showing a damping force map
describing a relationship between a stroke speed SV and a target
damping force that changes accompanying with a change in the stroke
speed SV. FIG. 5A is an explanatory diagram conceptually
illustrating a pre/post-limitation target value map 61 according to
an embodiment that describes a relationship between forces before
and after limitation of the target damping force and the target
extension/contraction force when receiving a control current
limitation command signal. FIG. 5B is an explanatory diagram
conceptually illustrating a pre/post-limitation target value map 63
according to a modification that describes a relationship between
forces before and after limitation of the target damping force and
the target extension/contraction force when receiving the control
current limitation command signal.
[0043] The ECU 15 includes a microcomputer configured to perform
various arithmetic processing. The ECU 15 has a drive control
function of generating a driving force used for vibration damping
of the vehicle by controlling driving of each of the plurality of
electromagnetic actuators 13, for example, based on a rotation
angle of the electric motor 31 detected by the resolver 37.
[0044] In order to achieve such a driving-control function, as seen
in FIG. 3, the ECU 15 includes an information acquisition part 43,
a driving force calculator 47, and a drive controller 49.
[0045] In the present embodiment, the ECU 15 corresponds to the
"drive control unit" described in CLAIMS of the present
invention.
[0046] As shown in FIG. 3, the information acquisition part 43
acquires the rotation angle signal of the electric motor 31
detected by the resolver 37 as time-series information relating to
a stroke position, and acquires information on a stroke velocity SV
by time-differentiating the time-series information of the stroke
position.
[0047] Further, as shown in FIG. 3, the information acquisition
part 43 acquires information on the ECU temperature Te detected by
an ECU temperature sensor 44 provided on, for example, a substrate
of the ECU 15, and information of the motor temperature Tm detected
by a motor temperature sensor 46 provided on, for example, the
housing of the electric motor 31.
[0048] However, the information on the ECU temperature Te
(including the information on an ambient temperature around the ECU
15) is used by a driving force calculator 47B according to a first
modification described below. Further, the information on the motor
temperature Tm (including information on the ambient temperature
around the electric motor 31) is used by a driving force calculator
47C according to a second modification described below. Therefore,
the information acquisition part 43 included in the electrically
powered suspension system 11 according to the embodiment can omit
the acquisition of the information on the ECU temperature Te and
the motor temperature Tm.
[0049] Further, as shown in FIG. 3, the information acquisition
part 43 acquires time-series information on sprung acceleration
detected by a sprung acceleration sensor 40; and information on a
sprung speed BV by time-integrating the time-series information on
the sprung acceleration.
[0050] Further, as shown in FIG. 3, the information acquisition
part 43 acquires vehicle speed information detected by the vehicle
speed sensor 41, yaw rate information detected by the yaw rate
sensor 42, and information on a motor current supplied to the
electric motor 31 to achieve the target driving force of the
electromagnetic actuator 13.
[0051] The above types of the information acquired through the
information acquisition part 43, such as the information on the
stroke speed SV, the information on the ECU temperature and the
motor temperature, the information on the sprung speed BV, the
information on the vehicle speed, the information on the yaw rate,
and the information on the motor current, are respectively sent to
the driving force calculator 47.
[0052] The driving force calculator 47A of the embodiment, as shown
in FIG. 4A, includes a target damping force setting part 51, a
target damping force limiting part 52, a target
extension/contraction force setting part 53, a target
extension/contraction force limiting part 54, a state determination
part 55, and an adder 57.
[0053] The driving force calculator 47A of the embodiment basically
works to calculate respectively a target damping force that is a
target value of the vibration damping of the electromagnetic
actuator 13; and a target extension/contraction force that is a
target value of the extension/contraction operation, and to
calculate a target driving force necessary for the vibration
damping and the extension/contraction of the electromagnetic
actuator 13 so as to achieve the target damping force and target
extension/contraction force calculated.
[0054] Here, the driving force calculator 47A of the embodiment
performs state determination on whether or not the electric motor
31 is in an excessive heat generation state based on information of
a integrated motor current value Iint (detailed below) acquired by
performing time-integration of time-series information on the motor
current.
[0055] However, the state determination on whether or not the
electric motor 31 is in the excessive heat generation state may be
performed based on the information on the ECU temperature Te
acquired in a predetermined cycle (detailed below as the driving
force calculator 47B according to the first modification), or
performed based on the information on the motor temperature Tm
acquired in a predetermined cycle (detailed below as the driving
force calculator 47C according to the second modification).
[0056] Furthermore, the state determination on whether or not the
electric motor 31 is in the excessive heat generation state may be
performed based on information on an ECU temperature integrated
value Teint acquired by time-integrating the time series
information relating to the ECU temperature Te acquired in a
predetermined cycle; or based on information of a motor temperature
integrated value Tmint acquired by time-integrating the time-series
information on the motor temperature Tm acquired at a predetermined
cycle.
[0057] Note that in the present specification, the driving force
calculator 47A of the embodiment, the driving force calculator 47B
according to the first modification, and the driving force
calculator 47C according to the second modification are
collectively referred to as "driving force calculator 47".
[0058] The driving force calculator 47 of the present embodiment
corresponds to a "current calculator" of Claims of the present
invention.
[0059] More specifically, the target damping force setting part 51
provided in the driving force calculator 47A of the embodiment
configures a value of the target damping force responsive to the
stroke speed SV based on the information on the stroke speed SV
acquired via the information acquisition part 43 and a target
damping force map 51A (see FIG. 4B) conceptually representing a
relationship between the target damping force and the stroke speed
in which the target damping force varies in response to variations
of the stroke speed. The target damping force map 51A stores in an
actual implementation a target value of a damping force control
current (a value of the target damping current) as a value
corresponding to the value of the target damping force.
[0060] As seen in FIG. 4B, a domain of the stroke velocity SV of
the target damping force map 51 includes a normal use region SV1
and non-normal use regions SV2. The normal use region SV1 is a
velocity region in which a magnitude of the stroke velocity SV is
equal to or smaller than a normal use velocity threshold SVTh
(|SV|-SVTh.ltoreq.0). During the regular running of the vehicle,
most values of the stroke velocity SV converge into the normal use
region SV1.
[0061] The normal use velocity threshold SVTh may be configured to
an appropriate value by consulting an evaluation result acquired by
evaluating a probability density function of the stroke velocity SV
through experiments, simulations, and the like; and by considering
that a predetermined distribution ratio is satisfied by a
distribution ratio of the stroke velocity SV appearing respectively
in the normal use region SV1 and the non-normal use regions
SV2.
[0062] As seen in FIG. 4B, a target damping force characteristic
relating to the target damping force map 51A in the normal use
region SV1 has a characteristic such that the target damping force
directed toward a contraction direction increases substantially
linearly as the stroke velocity SV increases toward an extension
direction, whereas the target damping force directed toward the
extension direction increases substantially linearly as the stroke
velocity SV increases toward the contraction direction. This
characteristic is made similar to a damping characteristic of a
conventionally used hydraulic damper. Note that the corresponding
target damping force is also zero when the stroke velocity SV is
zero.
[0063] A target damping force characteristic of the non-normal use
region SV2 in the target damping force map 51A, as seen in FIG. 4B,
similarly to the target damping force characteristic of the normal
use region SV1 in the target damping force map 51A, has a
characteristic such that the target damping force directed toward
the contraction direction increases substantially linearly as the
stroke velocity SV increases toward the extension direction,
whereas the target damping force directed toward the extension
direction increases substantially linearly as the stroke velocity
SV increases toward the contraction direction.
[0064] However, as seen in FIG. 4B, the target damping force
characteristic in the non-normal use region SV2 of the target
damping force map 51A is configured to have a gentle slope as
compared with a slope of the target damping force characteristic in
the normal use region SV1 of the target damping force map 51A.
[0065] On the other hand, the target extension/contraction force
setting part 53 provided in the driving force calculator 47A of the
embodiment configures a value of the target extension/contraction
force responsive to the sprung speed BV acquired by the information
acquisition part 43 and a target extension/contraction force map
53A (see FIG. 4C) conceptually representing a relationship between
the sprung speed BV and the target extension/contraction force that
varies accompanying with variations of the sprung speed BV. Note
that the target extension/contraction force map in an actual
implementation stores a target value of an extension/contraction
control current (a value of the target extension/contraction
current) as a value corresponding to the target
extension/contraction force.
[0066] As shown in FIG. 4C, the target extension/contraction force
characteristic according to the target extension/contraction force
map 53A exhibits a characteristic in which the target
extension/contraction force directed toward a contraction direction
increases linearly as the sprung speed BV increases toward the
extension direction, while the target extension/contraction force
directed toward an extension direction linearly increases as the
sprung speed BV increases toward the contraction direction.
[0067] Note that the target extension/contraction force
characteristic according to the target extension/contraction force
map 53A may be acquired by performing experiments/simulations and
the like for acquiring the target extension/contraction force
responsive to the sprung speed BV in order to keep a posture of the
vehicle 10 in a predetermined state; and configure an appropriate
characteristic value acquired by the experiments/simulations, etc.
as appropriate.
[0068] The state determination part 55 provided in the driving
force calculator 47A of the embodiment acquires the time-series
information of the motor current via the information acquisition
part 43, and the information of the integrated motor current value
Iint by time-integrating the time-series information of the motor
current. A range (time length) to be subjected to the
time-integration may be configured to an appropriate time length
(for example, three to ten minutes retroactively) in consideration
of a heat capacity, heat radiation characteristics, and the like of
the electric motor 31.
[0069] Further, the state determination part 55 performs a state
determination on whether or not the integrated motor current value
Iint exceeds a integrated current threshold Iint_th, that is,
whether or not the electric motor 31 is in an excessive heat
generation state, based on information such as the information of
the integrated motor current value Iint acquired.
[0070] If the state determination result is that the integrated
motor current value Iint exceeds the integrated current threshold
Iint_th, that is, the electric motor 31 is in the excessive heat
generation state, the state determination part 55 sends a control
current limiting command signal indicating that the control current
for achieving the driving force used for the damping and
extension/contraction forces is to be limited respectively to the
target damping force limiting part 52 and the target
extension/contraction force limiting part 54.
[0071] Upon receiving the control current limiting command signal
that is sent from the state determination part 55, the target
damping force limiting part 52 calculates a value of a target
damping force after limitation (target damping current) based on
the value of the target damping force set by the target damping
force setting part 51 and the pre/post-limitation target value maps
61A (see FIGS. 4A and 5A) according to the embodiment conceptually
showing the relationship between values before and after target
values of the damping force and the extension/contraction force are
limited when the target damping force setting part 51 receives the
control current limiting command signal. Note that the
pre/post-limitation target value map 61A stores actually a target
value of the damping force control current (value of target damping
current) as a value equivalent to the value of the target damping
force after limitation.
[0072] On the other hand, the target extension/contraction force
limiting part 54, upon receiving the control current limiting
command signal sent from the state determination part 55,
calculates a value of a target extension/contraction force after
limitation (target extension/contraction current) based on the
value of the target extension/contraction force set by the target
extension/contraction force setting part 53 and the
pre/post-limitation target value map 61B (see FIGS. 4A and 5A)
according to the embodiment. Note that the pre/post-limitation
target value map 61 stores actually a target value of the
extension/contraction force control current (value of target
extension/contraction current) as a value equivalent to the value
of the target extension/contraction force after limitation.
[0073] Here, the pre/post-limitation target value map 61A according
to the embodiment, to which the target damping force limitation
part 52 refers when calculating the value of the target damping
force (target damping current) after limitation, and the
pre/post-limitation target value map 61B according to the
embodiment, to which the target extension/contraction force
limitation part 54 refers when calculating the value of the target
extension/contraction force (target extension/contraction current)
after limitation, may be configured as commonly accessible
information, or may be configured as separate information.
[0074] The following description is given of an example in which
the pre/post-limitation target value maps 61A and 61B (these are
collectively referred to as "pre/post-limitation target value map
61") according to the embodiment are configured as commonly
accessible information.
[0075] Further, the calculation of the target damping force after
limitation calculated by the target damping force limitation part
52 and the calculation of the target extension/contraction force
after limitation by the target extension/contraction force
limitation part 54 are performed independently. As a result, a
calculation result of the target damping force after limitation
calculated by the target damping force limitation part 52 and a
calculation result of the target extension/contraction force after
limitation by the target extension/contraction force limitation
part 54 have respectively independent values.
[0076] As shown in FIG. 4A, the adder 57 provided in the driving
force calculator 47A of the embodiment adds the target damping
force after limitation calculated by the target damping force
limitation part 52 and the target extension/contraction force after
limitation calculated by the target extension/contraction force
limitation part 54 to acquire the target driving force and further
acquires a driving control signal for achieving the target driving
force by calculation. The drive control signal, which is a
calculation result acquired by the driving force calculator 47A of
the embodiment, is sent to the drive controller 49.
[0077] The drive controller 49 performs drive control of each of
the plurality of the electromagnetic actuators 13 separately by
supplying a drive control power to the electric motor 31 provided
in each of the plurality of electromagnetic actuators 13 in
accordance with the drive control signal sent from the driving
force calculator 47A of the embodiment.
[0078] Note that generating the drive control power to be supplied
to the electric motors 31 may use, for example, an inverter control
circuit as appropriate.
Pre/Post-Limitation Target Value Map 61 According to Embodiment
[0079] Next, description is given of the pre/post-limitation target
value map 61 according to the embodiment.
[0080] In the pre/post-limitation target value map 61 according to
the embodiment, a domain TVB of pre-limitation target value
(hereinbelow, sometimes abbreviated as "pre-limitation target
value") includes, as indicated on a horizontal axis of FIG. 5A, the
first pre-limitation target value TVb1, the second pre-limitation
target value TVb2, and the third pre-limitation target value TVb3
(where TVb1>TVb2>TVb3).
[0081] The domain TVB of the pre-limitation target value includes a
first domain TVB-1 from zero to a first pre-limitation target value
TVb1; a second domain TVB-2 from zero to a second pre-limitation
target value TVb2; and a third domain TVb-3 from zero to a third
pre-limitation target value TVb3.
[0082] On the other hand, a value range TVA of a post-limitation
target value includes a first post-limitation target value TVa1, a
second post-limitation target value TVa2, and a third
post-limitation target value TVa3 configured as
TVa1>TVa2>TVa3, as shown in a vertical axis of FIG. 5A.
[0083] The value range TVA relating to the post-limitation target
value includes a first value range TVA-1 from zero to the first
post-limitation target value TVa1, a second value range TVA-2 from
zero to the second post-limitation target value TVa2, and a third
value range TVA-3 from zero to the third post-limitation target
value TVa3.
[0084] The domain TVB of the pre-limitation target value and the
value range TVA of the post-limitation target value are associated
with each other via a predetermined function.
[0085] Note that the first to sixth domains TVB-1 to TVB-6 relating
to the pre-limitation target values may be simply referred to as
the domain TVB of the pre-limitation target value when there is no
need to individually specify them.
[0086] Further, the first to three value ranges TVA-1 to TVA-3
relating to the post-limitation target value may be simply referred
to as the value range TVA relating to the post-limitation target
value when there is no need to individually specify them.
[0087] More specifically, the first to third domains TVB-1, TVB-2,
and TVB-3 (detailed below) of the pre-limitation target values are
respectively associated with the first to third value ranges TVA-1,
TVA-2, and TVA-3 (detailed below) of the post-limitation target
value via a predetermined (commonly configured) linear function F1
along with a vertical axis of FIG. 5A.
[0088] On the other hand, the fourth to sixth domains TVB-4, TVB-5,
and TVB-6 (detailed below) of the pre-limitation target values are
associated respectively with the first to third post-limitation
target values: fixed values TVa1, TVa2, and TVa3
(TVa1>TVa2>TVa3) via respective many-to-one functions as
shown in the vertical direction of FIG. 5A.
[0089] The first domain TVB-1 is a domain relating to the target
values before limitation of the damping force and the
extension/contraction force in the normal state in which the
electric motor 31 is not in the excessive heat generation
state.
[0090] The pre-limitation target values of the damping force and
the extension/contraction force belonging to the first domain TVB-1
can be mapped with one-to-one association to the post-limitation
target values of the damping force and the extension/contraction
force belonging to the first value range TVA-1 using the
predetermined linear function F1. For example, the first
pre-limitation target value TVb1 can be mapped to the first
post-limitation target value TVa1.
[0091] The second domain TVB-2 is a domain relating to the
pre-limitation target value of the damping force at a time of
abnormality when the electric motor 31 is in the excessive heat
generation state.
[0092] At the time of abnormality, the pre-limitation target value
of the damping force belonging to the second domain TVB-2 is mapped
with one-to-one association to the post-limitation target values of
the damping force belonging to the second value range TVA-2 via a
predetermined linear function F1. For example, the second
pre-limitation target value TVb2 of the damping force is mapped to
the second post-limitation target value TVa2 of the damping
force.
[0093] The second domain TVB-3 is a domain relating to the
pre-limitation target value of the damping force at a time of
abnormality when the electric motor 31 is in the excessive heat
generation state.
[0094] At the time of abnormality, the pre-limitation target value
of the damping force belonging to the second domain TVB-3 is mapped
with one-to-one association to the post-limitation target values of
the damping force belonging to the second value range TVA-3 via a
predetermined linear function F1. For example, the second
pre-limitation target value TVb3 of the damping force is mapped to
the second post-limitation target value TVa3 of the damping
force.
[0095] Further, as shown on the horizontal axis of FIG. 5A, the
domain TVB of the pre-limitation target value includes the fourth
domain TVB-4 exceeding the first pre-limitation target value TVb1,
and the fifth domain TVB-5 exceeding the second pre-limitation
target value TVb2, and the sixth domain TVB-6 exceeding the third
pre-limitation target value TVb3.
[0096] The fourth domain TVB-4 is, similarly to the first domain
TVB-1, a domain relating to the target values before limitation of
the damping force and the extension/contraction force at the normal
time when the electric motor 31 is not in the excessive heat
generation state. However, the fourth domain TVB-4 differs from the
first domain TVB-1 in that the fourth domain TVB-4 occupies a
domain relating to the pre-limitation target value having the
larger target value than that of the first domain TVB-1. A
combination of the first domain TVB-1 and the fourth domain TVB-4
is included by a domain relating to the target values before
limitation of the damping force and the extension/contraction force
in the normal time.
[0097] In the normal time, the target values before limitation of
the damping force and the extension/contraction force that belong
to the fourth domain TVB-4 are mapped to the first post-limitation
target value TVa1 of the damping force and the
extension/contraction force that are the fixed target value via the
predetermined many-to-one function. The purpose of the above
configuration is to limit the post-limitation target value to a
levelled value irrespective of an increase in the pre-limitation
target value in order to suppress an endless increase in the
damping force and the extension/contraction force by setting the
post-limitation target value to a fixed value: the first
post-limitation target value TVa1 in the fourth domain TVB-4 having
the larger pre-limitation target value than the first domain
TVB-1.
[0098] The fifth domain TVB-5 is, similarly to the second domain
TVB-2, a domain relating to the pre-limitation target value of the
damping force when the electric motor 31 is in an abnormal state in
which an excessive heat is generated. However, the fifth domain
TVB-5 differs from the second domain TVB-2 in that the fifth domain
TVB-5 occupies a domain relating to the pre-limitation target value
having the larger target value than that of the second domain TVB-2
in the domain relating to the pre-limitation target value. A
combination of the second domain TVB-2 and the fifth domain TVB-5
is included by a domain relating to the target values before
limitation of the damping force in the time of abnormality.
[0099] At the time of abnormality, the target values before
limitation of the damping force belonging to the fifth domain TVB-5
are mapped to the second post-limitation target value TVa2 of the
damping force that are the fixed value via the predetermined
many-to-one function (see the solid line portion indicating the
target damping force characteristic after limitation in the
pre/post-limitation target value map 61 according to the embodiment
shown in FIG. 4A). The purpose of the above configuration is to
limit the post-limitation target value to a levelled value
irrespective of an increase in the pre-limitation target value to
suppress an endless increase in the damping force by setting the
post-limitation target value to a fixed value: the second
post-limitation target value TVa2, in the fifth domain TVB-5 having
the larger pre-limitation target value than the second domain
TVB-2.
[0100] The sixth domain TVB-6 is, similarly to the third domain
TVB-3, a domain relating to the pre-limitation target value of the
extension/contraction force when the electric motor 31 is in an
abnormal state in which an excessive heat is generated. However,
the sixth domain TVB-6 differs from the third domain TVB-3 in that
the sixth domain TVB-6 occupies a domain relating to the
pre-limitation target value having the larger target value than
that of the third domain TVB-3 in the domain relating to the
pre-limitation target value. A combination of the third domain
TVB-3 and the sixth domain TVB-6 is included by a domain relating
to the target values before limitation of the extension/contraction
force in the time of abnormality.
[0101] At the time of abnormality, the target values before
limitation of the extension/contraction force that belong to the
sixth domain TVB-6 are mapped to the third post-limitation target
value TVa3 of the extension/contraction force that are the fixed
value via the predetermined many-to-one function (see the solid
line portion indicating the target extension/contraction force
characteristic after limitation in the pre/post-limitation target
value map 61 according to the embodiment shown in FIG. 4A. The
purpose of the above configuration is to limit the post-limitation
target value to a levelled value irrespective of an increase in the
pre-limitation target value to suppress an endless increase in the
extension/contraction force by setting the post-limitation target
value to a fixed value: the third post-limitation target value TVa3
in the sixth domain TVB-6 having the larger pre-limitation target
value than the third domain TVB-3.
[0102] The pre/post-limitation target value map 61 according to the
embodiment, as shown in FIGS. 4A and 5A, describes how the target
values before limitation of the damping force and the
extension/contraction force are mapped to the post-limitation
target values of the damping force and the extension/contraction
force in the normal state: when the electric motor 31 is not in the
excessive heat generation state and in the abnormal state: when the
electric motor 31 is in an excessive heat generation state.
[0103] That is, in the normal state, the pre-limitation target
values of the damping force and the extension/contraction force
belonging to the first domain TVB-1 are mapped to the
post-limitation target values of the damping force and the
extension/contraction force belonging to the first value range
TVA-1 using the predetermined linear function F1; and the
pre-limitation target values of the damping force and the
extension/contraction force belonging to the fourth domain TVB-4
are mapped to the fixed first post-limitation target values TVa1 of
the damping force and the extension/contraction force through a
predetermined many-to-one function.
[0104] The operation at the time of abnormality, which is paired
with the normal time, is described separately about the damping
force and the extension/contraction force.
[0105] First, about the damping force at the time of abnormality,
description is given of how the pre-limitation target value is
mapped to the post-limitation target value.
[0106] At the time of abnormality, the pre-limitation target value
of the damping force belonging to the second domain TVB-2 is mapped
to the post-limitation target value of the damping force belonging
to the second value range TVA-2 through the predetermined linear
function F1, and the pre-limitation target value of the damping
force belonging to the fifth domain TVB-5 is mapped to the fixed
post-limitation target value TVa2 of the damping force through the
predetermined many-to-one function.
[0107] Next, about the extension/contraction force at the time of
abnormality, description is given of how the post-limitation target
value is mapped to the pre-limitation target value.
[0108] At the time of abnormality, the pre-limitation target value
of the extension/contraction force belonging to the third domain
TVB-3 is mapped to a post-limitation target value of the
extension/contraction force belonging to the third value range
TVA-3 through a predetermined linear function F1; and the
pre-limitation target value of the extension/contraction force
belonging to the sixth domain TVB-6 is mapped to a fixed
post-limitation target value TVa3 of the extension/contraction
force through a predetermined many-to-one function.
[0109] In another aspect of view, FIG.5A shows that the
pre/post-limitation target value map 61 according to the embodiment
is configured so that the post-limitation target value of the
extension/contraction force at the time of abnormality
(extension/contraction current limitation threshold: the third
post-limitation target value TVa3) is smaller than the
post-limitation target value of the damping force at the time of
the abnormality (damping current limitation threshold: the second
post-limitation target value TVa2).
<Pre/Post-Limitation Target Value Map 63 of Modification>
[0110] Next, description is given of the pre/post-limitation target
value map 63 according to a modification with reference to FIG.
5B.
[0111] FIG. 5B is an explanatory diagram of a pre/post-limitation
target value map 63 according to a modification that conceptually
illustrates a relationship between the target values before and
after limitation of the damping force and the extension/contraction
force when receiving the control current limiting command
signal.
[0112] The pre/post-limitation target value map 61 according to the
embodiment shown in FIG. 5A and the pre/post-limitation target
value map 63 according to the modification shown in FIG. 5B have
many common characteristics.
[0113] Therefore, description is given of the pre/post-limitation
target value map 63 according to the modification by focusing on
differences between the pre/post-limitation target value map 61
according to the embodiment and the pre/post-limitation target
value map 63 according to the modification and by describing mainly
the differences.
[0114] In the pre/post-limitation target value map 63 according to
the modification, a domain TVB of the pre-limitation target value
has the eleventh pre-limitation target value TVb11, the twelfth
pre-limitation target value TVb12, and the thirteenth
pre-limitation target value TVb13 respectively configured so that
their values are as TVb11<TVb12<TVb13.
[0115] The domain TVB of the pre-limitation target value includes
an eleventh domain TVB-11 from zero to the eleventh pre-limitation
target value TVb11, a twelfth domain TVB-12 from zero to the
twelfth pre-limitation target value TVb12, and a thirteenth domain
TVB-13 from zero to the thirteenth pre-limitation target value
TVb13.
[0116] On the other hand, the value range TVA relating to the
post-limitation target value has an eleventh post-limitation target
value TVa11, a twelfth post-limitation target value TVa12, and a
thirteenth post-limitation target value TVa13 respectively
configured so that their values are as TVa11>TVa12>TVa13, as
indicated on the vertical axis in FIG. 5B.
[0117] The value range TVA relating to the post-limitation target
value includes an eleventh value range TVA-11 from zero to the
eleventh post-limitation target value TVa11, a twelfth value range
TVA-12 from zero to the twelfth post-limitation target value TVa12,
and a thirteenth value range TVA-13 from zero to the thirteenth
post-limitation target value TVa13.
[0118] The domain TVB of the pre-limitation target value and the
range TVA of the post-limitation target value are associated with
each other respectively through predetermined different functions
F11, F12, and F13.
[0119] A difference of the pre/post-limitation target value map 63
according to the modification from the pre/post-limitation target
value map 61 according to the embodiment is that the domain TVB of
the pre-limitation target value and the value range TVA relating to
the post-limitation target value are associated with each other
respectively through the predetermined different functions F11,
F12, and F13.
[0120] More specifically, the eleventh to thirteenth domains
TVB-11, TVB-12, and TVB-13 relating to the pre-limitation target
value are mapped respectively to the eleventh to thirteenth value
ranges TVA-11, TVA-12, and TVA-13 of the post-limitation target
value respectively through the different predetermined functions
F11, F12, and F13 along the vertical axis of FIG. 5B.
[0121] The eleventh domain TVB-11 is a domain relating to the
pre-limitation target values of the damping force and the
extension/contraction force at the normal time when the electric
motor 31 is not in the excessive heat generation state.
[0122] The pre-limitation target values of the damping force and
the extension/contraction force belonging to the eleventh domain
TVB-11 are mapped with one-to-one association to the
post-limitation target values of the damping force and the
extension/contraction force belonging to the eleventh value range
TVA-11 using the predetermined linear function F11. For example,
the eleventh pre-limitation target value TVb11 is mapped to the
eleventh post-limitation target value TVa11.
[0123] The twelfth domain TVB-12 is a domain relating to the
pre-limitation target value of the damping force at the time of
abnormality when the electric motor 31 is in the excessive heat
generation state.
[0124] In the time of abnormality, the pre-limitation target value
of the damping force belonging to the twelfth domain TVB-12 is
mapped through one-to-one association to the post-limitation target
value of the damping force belonging to the twelfth value range
TVA-12 through the predetermined linear function F12.
[0125] The predetermined linear function F12 is configured to have
a gentler slope than the predetermined linear function F11. For
example, the twelfth pre-limitation target value TVb12 of the
damping force is mapped to the twelfth post-limitation target value
TVa12 of the damping force, which TVa12 is smaller than TVa11.
[0126] The thirteenth domain TVB-13 is a domain relating to the
pre-limitation target value of the extension/contraction force at
the time of abnormality when the electric motor 31 is in the
excessive heat generation state.
[0127] In the time of abnormality, the pre-limitation target value
of the extension/contraction force belonging to the thirteenth
domain TVB-13 is mapped through one-to-one association to the
post-limitation target value of the extension/contraction force
belonging to the thirteenth value range TVA-13 through the
predetermined linear function F13.
[0128] The predetermined linear function F13 is configured to have
a gentler slope than the predetermined linear function F12. For
example, the thirteenth pre-limitation target value TVb13 of the
extension/contraction force is mapped to the thirteenth
post-limitation target value TVa13 of the extension/contraction
force, which TVa13 is smaller than TVa12.
[0129] In short, the pre/post-limitation target value map 63
according to the modification differs from the pre/post-limitation
target value map 61 in that slopes of the linear functions used to
map the pre-limitation target value to the post-limitation target
value are gentler (F11>F12>F13) as an operation mode of the
electric motor 31 shifts from the damping and extension/contraction
control in the normal time, through the damping control at the time
of abnormality, and to the extension/contraction control at the
time of abnormality in a region of the domain TVB of the
pre-limitation target value in which pre-limitation target values
at the respective operation modes are smaller than the respective
pre-limitation target values TVb11, TVb12, and TVb13.
[0130] Note that, the pre/post-limitation target value map 63
according to the modification has the domains occupying a larger
pre-limitation target value respectively than the eleventh domain
TVB-11, the twelfth domain TVB-12, and the thirteenth domain TVB-13
are mapped to respective fixed values (the eleventh post-limitation
target value TVa11, the twelfth post-limitation target value TVa12,
and the thirteenth post-limitation target value TVa13), to suppress
an endless increase in the damping force and the
extension/contraction force by setting the post-limitation target
value to a fixed levelled value. This configuration is the same as
the pre/post-limitation target value map 61 according to the
embodiment.
[0131] Note that, the pre/post-limitation target value map 63
according to the modification may be configured to have domain
portions having the larger pre-limitation target value respectively
than the eleventh domain TVB-11, the twelfth domain TVB-12, and the
thirteenth domain TVB-13 mapped to a common fixed value (for
example, the eleventh post-limitation target value TVa11) as the
post-limitation target value, so that the post-limitation target
values are levelled off irrespective of increases of the
pre-limitation target values in the respective domains in order to
suppress endless increases of the damping force and the
extension/contraction force.
[0132] Note that the pre/post-limitation target value map 63
according to the modification has the post-limitation target value
of the extension/contraction force at the time of abnormality (the
extension/contraction current limitation threshold, i.e., the
thirteenth post-limitation target value TVa13) set to a value
smaller than the post-limitation target value of the damping force
at the time of abnormality (the damping current limitation
threshold, i.e., the twelfth post-limitation target value TVa12),
similarly to the pre/post-limitation target value map 61 according
to the embodiment.
Operation of Electrically Powered Suspension System 11 According to
Embodiment
[0133] Next, description is given of an operation of the
electrically powered suspension system 11 according to the
embodiment of the present invention with reference to FIG. 6, which
is a flowchart illustrating the operation of the electrically
powered suspension system 11 according to the embodiment of the
present invention.
[0134] In step S11: "Acquire stroke speed" shown in FIG. 6, the
information acquisition part 43 of the ECU 15 receives a rotation
angle signal of the electric motor 31 detected by the resolver 37
as time-series information on a stroke position, and
time-differentiates this time-series information to acquire
information on a stroke speed SV. The information on the stroke
speed SV acquired in this manner is sent to the driving force
calculator 47.
[0135] In step S12: "Acquire sprung speed", the information
acquisition part 43 of the ECU 15 acquires time-series information
on sprung acceleration detected by the sprung acceleration sensor
40 and time-integrates the time-series information on the sprung
acceleration to acquire information on a sprung speed BV. The
information on the sprung speed BV acquired in this way is sent to
the driving force calculator 47.
[0136] In step S13: "Calculate target damping force and target
extension/contraction force", the target damping force setting part
51 provided in the driving force calculator 47 of the ECU 15
determines a value of a target damping force responsive to the
stroke speed SV based on the information on the stroke speed SV
acquired in step S11 and a target damping force map 51A (see FIG.
4B) conceptually representing a relationship (target damping force
characteristic) between the stroke speed SV and a target damping
force that varies responding to variations of the stroke speed
SV.
[0137] Further, the target extension/contraction force setting part
53 provided in the driving force calculator 47 of the ECU 15
determines a value of the target extension/contraction force
responsive to the sprung speed BV based on the information on the
sprung speed BV acquired in step S12 and a target
extension/contraction force map conceptually representing a
relationship (target extension/contraction force characteristics)
between the sprung speed BV and the target extension/contraction
force that varies in response to the variations of the sprung speed
BV.
[0138] In step S14, the state determination part 55 included in the
driving force calculator 47 of the ECU 15, first calculates a
integrated motor current value Iint by time-integrating time-series
information on the motor current; next, performs a state
determination as to whether or not the integrated motor current
value Iint exceeds the integrated current threshold Iint_th, that
is, whether or not the electric motor 31 is in the excessive heat
generation state, on a basis of the information on the calculated
integrated motor current value Iint, and the like.
[0139] When the state determination in step S14 results in a
determination that the electric motor 31 is not in the excessive
heat generation state ("No" in step S14), the ECU 15 makes the
processing flow jump to step S161.
[0140] On the other hand, when the state determination in step S14
results in a determination that the electric motor 31 is in the
excessive heat generation state ("Yes" in step S14), the state
determination part 55 included in the driving force calculator 47
of the ECU 15 sends a setting-permission signal indicating a
permission of the setting according to setting information on a
control mode respectively to the target damping force limitation
part 52 and the target extension/contraction force limitation part
54.
[0141] In step S15, the target damping force limiting part 52
included in the driving force calculator 47 of the ECU 15
calculates a value of the post-limitation target damping force on a
basis of the value of the target damping force set in the step S13
and the pre/post-limitation target value map 61 according to the
embodiment.
[0142] Further, the target extension/contraction force limiting
part 54 included in the driving force calculator 47 of the ECU 15
calculates a post-limitation target value of the
extension/contraction force on a basis of the value of the target
extension/contraction force determined in step S13 and the
pre/post-limitation target value map 61 according to the
embodiment.
[0143] In step S16: "Calculate driving force", if the state
determination in step S14 results in the determination that the
electric motor 31 is in the excessive heat generation state, the
adder 57 included in the driving force calculator 47 of the ECU 15
calculates a target driving force by adding the post-limitation
target damping force calculated by the target damping force
limitation part 52 and the target extension/contraction force
calculated by the target extension/contraction force limitation
part 54 both in the step S15; and calculates a driving control
signal for achieving the target driving force.
[0144] However, when the state determination in step S14 results in
the determination that the electric motor 31 is not in the
excessive heat generation state, the adder 57 included in the
driving force calculator 47 of the ECU 15 acquires a target driving
force by adding the target damping force calculated by the target
damping force setting part 51 and the target extension/contraction
force calculated by the target extension/contraction force
limitation part 53 both in the step S13; and calculates a drive
control signal for achieving the target driving force.
[0145] In step S17, the drive controller 49 of the ECU 15 supplies
drive control power to the electric motor 31 provided in each of
the plurality of electromagnetic actuators 13 in accordance with
the drive control signal calculated in the step S16, so as to
perform the drive control of the plurality of electromagnetic
actuators 13.
<Internal Configuration of Driving Force Calculator According to
First Modification>
[0146] Next, description is given of an internal configuration of a
driving force calculator 47B according to first modification
included in the ECU 15 of the electrically powered suspension
system 11 with reference to FIG. 7A.
[0147] FIG. 7A is a block diagram conceptually illustrating the
internal configuration of the driving force calculator 47B
according to a first modification included in the ECU 15 of the
electrically powered suspension system 11.
[0148] The driving force calculator 47A of the embodiment
illustrated in FIG. 4A and the driving force calculator 47B
according to the first modification illustrated in FIG. 7A have
many components common to both.
[0149] Accordingly, description is given, which is focused mainly
on differences between the driving force calculator 47A of the
embodiment and the driving force calculator 47B according to the
first modification by focusing on them, which description
substitutes for an explanation on the driving force calculator 47B
according to the first modification.
[0150] The driving force calculator 47B according to the first
modification differs from the driving force calculator 47A of the
embodiment in that the driving force calculator 47B determines
whether or not the electric motor 31 is in the excessive heat
generation state on a basis of information such as ECU temperature
Te, instead of the information of the integrated motor current
value Iint (used in the embodiment) acquired by time-integrating
the time-series information on the motor current.
[0151] The state determination part 55 included in the driving
force calculator 47B according to the first modification acquires
the information on the ECU temperature Te through the information
acquisition part 43. The information on the ECU temperature Te,
which varies every moment in response to a load state (drive
current) of the electric motor 31, may be acquired at a
predetermined cycle and used as appropriate.
[0152] Further, the state determination part 55 performs a state
determination of whether or not the ECU temperature value Te
exceeds the ECU temperature threshold Te_th, that is, whether or
not the electric motor 31 is in the excessive heat generation
state.
[0153] If the state of the determination results in a determination
that the ECU temperature Te exceeds the ECU temperature threshold
Te_th, that is, the electric motor 31 is in the excessive heat
generation, the state determination part 55 is sends a control
current limiting command signal indicating to limit the control
current for achieving the driving force relating to the damping
force and the extension/contraction force, respectively to the
target damping force limiting part 52 and the target
extension/contraction force limiting part 54.
[0154] The subsequent operation is the same as that of the driving
force calculator 47A of the embodiment.
<Internal Configuration of Driving Force Calculator of Second
Modification>
[0155] Next, description is given of an internal configuration of a
driving force calculator 47C according to second modification
provided in the ECU 15 of the electrically powered suspension
system 11 with reference to FIG. 7B.
[0156] FIG. 7B is a block diagram conceptually illustrating an
internal configuration of the driving force calculator 47C
according to the second modification provided in the ECU 15 of the
electrically powered suspension system 11.
[0157] The driving force calculator 47A of the embodiment
illustrated in FIG. 4A and the driving force calculator 47C
according to the second modification illustrated in FIG. 7C have
many components common to both.
[0158] Accordingly, a description is given, which is focused mainly
on differences between the driving force calculator 47A of the
embodiment and the driving force calculator 47C according to the
second modification, and which description substitutes for an
explanation on the driving force calculator 47C according to the
second modification.
[0159] The driving force calculator 47C according to the second
modification is different from the driving force calculator 47A of
the embodiment in that the driving force calculator 47C performs a
state determination of whether or not the electric motor 31 is in
the excessive heat generation state on a basis of information such
as a motor temperature Tm instead of the information of the
integrated motor current value Iint (used in the embodiment)
acquired by time-integrating the time-series information of the
motor current.
[0160] The state determination part 55 included in the driving
force calculator 47C according to the second modification acquires
the information on the motor temperature Tm via the information
acquisition part 43. The information on the motor temperature Tm,
which varies every moment in response to a load state (drive
current) of the electric motor 31, may be acquired at a
predetermined cycle and used as appropriate.
[0161] Further, the state determination part 55 performs a state
determination of whether or not the motor temperature Tm exceeds
the motor temperature threshold Tm_th, that is, whether or not the
electric motor 31 is in the excessive heat generation state.
[0162] If the state of the determination results in a determination
that the Motor temperature Tm exceeds the motor temperature
threshold Tm_th, that is, the electric motor 31 is in the excessive
heat generation, the state determination part 55 sends a control
current limiting command signal indicating to limit the control
current for achieving the driving force relating to the damping
force and the extension/contraction force, respectively to the
target damping force limiting part 52 and the target
extension/contraction force limiting part 54.
[0163] The subsequent operation is the same as that of the driving
force calculator 47A of the embodiment.
Features of Electrically Powered Suspension System 11 of
Embodiment
[0164] Next, description is given of features of the electrically
powered suspension system 11 according to the embodiment (including
an example, and modifications 1 and 2) of the present
invention.
[0165] The first feature is that the damping current limitation
threshold and the extension/contraction current limitation
threshold (when the electric motor 31 is in an excessive heat
generation state) are configured individually in consideration of
conditions such that they are different in priority on riding
comfort and driving stability of the vehicle 10 and an energization
time for the damping control and the extension/contraction
control.
[0166] First, description is given of the priority regarding the
riding comfort and the driving stability of the vehicle 10.
[0167] The time of abnormality (when the electric motor 31 is in an
excessive heat generation state) may be supposed to be, for
example, a case in which requests frequently occur to generate the
damping force and the extension/contraction force relating to the
electrically powered suspension system 11 when the vehicle 10 is
traveling on a rough unpaved road.
[0168] In the case described above, when the vehicle 10 is
traveling on the rough unpaved road, it is a principle to give
priority to the driving stability of the vehicle 10 more than the
riding comfort thereof, because there is a higher demand for
stabilizing a behavior of the vehicle 10 as compared with a case in
which the vehicle 10 is traveling on a maintained and paved road.
This means that the damping control mainly relating to a steering
stability is performed with priority over the extension/contraction
control mainly relating to the riding comfort of the vehicle
10.
[0169] Next, description is given of a situation in which a
difference occurs in the energization time for the damping control
and the extension/contraction control.
[0170] Generally, a frequency of a vibration wave to be controlled
by the damping control is prone to be higher than a frequency of a
vibration wave to be controlled by the extension/contraction
control. This results in a tendency in which an energization time
for the damping control that is an energization time required for
the damping control of the vibration wave in a predetermined unit
cycle period is shorter than an energization time for the
extension/contraction control of the vibration wave in a
predetermined unit cycle (vibration wave to be controlled by
damping control is subsided in a shorter time than vibration wave
to be controlled by extension/contraction control).
[0171] Conversely, the frequency of the vibration wave to be
controlled by the extension/contraction control tends to be lower
than the frequency of the vibration wave to be controlled by the
damping control. This results in a tendency in which the
energization time for the extension/contraction control of the
vibration wave in the predetermined unit cycle is longer than the
energization time for the damping control that is the energization
time required for the damping control of the vibration wave in the
predetermined unit cycle period (vibration wave to be controlled by
extension/contraction control needs a longer time than vibration
wave to be controlled by damping control).
[0172] As described above, the energization time for the damping
control of the vibration wave per unit cycle tends to be shorter
(settled in a shorter time) than the energization time for the
extension/contraction control of the vibration wave per unit cycle.
That is, there is a substantial difference in the energization time
for the damping control and the extension/contraction control of
the vibration wave per unit cycle.
[0173] This means that a reasonable design is to assign different
length of times respectively to the energization time for the
damping control and the energization time for the
extension/contraction control in the time of abnormality in which
the electric motor 31 generates excessive heat, when considering
the current limitation timing (operation limitation timing) for the
damping control and the extension/contraction control.
[0174] Therefore, the electrically powered suspension system 11
according to the embodiment of the present invention is configured
to have a configuration in which settings are separately assigned
to the damping current limitation threshold and the
extension/contraction current limitation threshold, considering the
priority on the riding comfort and steering stability of the
vehicle 10, and a condition such as the substantial difference in
the energization times for performing the damping control and the
extension/contraction control.
[0175] Here, the damping current limitation threshold is a current
limitation threshold that is a guide value for limiting the drive
current (damping control current) of the electric motor 31 when
performing the damping control at the time of abnormality. The
damping current limitation threshold corresponds to the second
post-limitation target value TVa2.
[0176] In addition, the extension/contraction current limitation
threshold is a current limitation threshold that is a guide value
for limiting the drive current (extension/contraction control
current) of the electric motor 31 when performing the
extension/contraction control at the time of abnormality. The
extension/contraction current limitation threshold corresponds to
the third post-limitation target value TVa3.
[0177] As shown in FIG. 5A, the second feature is that the
extension/contraction current limitation threshold (third
post-limitation target value TVa3) is set to a value smaller than
the damping current limitation threshold (second post-limitation
target value TVa2), that is, TVa3<TVa2.
[0178] As described above, the energization time for the
extension/contraction control of the vibration wave per unit cycle
tends to be longer than the energization time for the damping
control of the vibration wave per unit cycle, which means that an
amount of work (heat quantity) for the extension/contraction
control of the vibration wave per unit cycle tends to be larger
than an amount of work (heat quantity) for the damping control of
the vibration wave per unit cycle.
[0179] This second feature allows to give priority to performing
the current limitation of the extension/contraction control that
involves the riding comfort of the vehicle 10 and tends to generate
a larger amount of heat than the damping control, over the current
limitation of the damping control, and at the same time, and to
make the current limitation of the damping control (involving
suppression of the unsprung vibration) difficult to start and
thereby to achieve the vibration control of the vehicle 10 without
disturbing a behavior of the vehicle 10 and without impairing the
riding comfort of the vehicle 10 as much as possible even if the
electric motor 31 provided in the electromagnetic actuator 13 is in
an excessive heat generation state.
Effects of Electrically Powered Suspension System 11 of
Embodiment
[0180] The electrically powered suspension system 11 according to
the first aspect includes the electromagnetic actuator 13 including
the electric motor 31 generating the driving force relating to the
vibration damping and the extension/contraction; a driving force
calculator (target current calculator) 47 calculating respectively
a target damping current for generating a target driving force
relating to the vibration damping and a target
extension/contraction current for generating a target driving force
relating to the extension/contraction; and a drive controller 49
performing the drive control of the electric motor using a drive
current based on the target damping current and the target
extension/contraction current.
[0181] The drive controller 49 performs the drive control of the
electric motor 31 using the drive current of the electric motor 31
limited not to exceed a preconfigured current limitation
threshold.
[0182] The current limitation threshold includes an damping current
limitation threshold for the target damping current (second
post-limitation target value TVa2) and the extension/contraction
current limitation threshold for the target extension/contraction
current (third post-limitation target value TVa3).
[0183] The damping current limitation threshold (second
post-limitation target value TVa2) and the extension/contraction
current limitation threshold (third post-limitation target value
TVa3) are individually configured.
[0184] In the electrically powered suspension system 11 according
to the first aspect, the drive controller 49 controls the electric
motor 31 using the drive current limited so that the drive current
of the electric motor 31 does not exceed a preset current
limitation threshold. Drive control is performed.
[0185] In the embodiment of the present invention, properties for
the drive current of the electric motor 31 corresponds respectively
to the integrated motor current value Iint in the embodiment, the
ECU temperature value Te in the first modification, and a motor
temperature value Tm in the second modification.
[0186] In the above correspondence, properties for the current
limitation threshold pre-configured to limit the drive current of
the electric motor 31 corresponds respectively to the integrated
current threshold Iint_th in the embodiment, the ECU temperature
threshold Te_th in the first modification, the motor temperature
threshold Tm_th in the second modification.
[0187] In other words, the electrically powered suspension system
11 according to the first aspect determines that the electric motor
31 is in an excessive heat generation state when the drive current
of the electric motor 31 (integrated motor current value Iint in
the embodiment, ECU temperature value Te in the first modification,
motor temperature value Tm in the second modification) exceeds the
preset current limitation threshold (integrated current threshold
Iint_th in the embodiment, ECU threshold temperature Te_th in the
first modification, motor temperature threshold Tm_th in the second
modification).
[0188] The current limitation threshold includes the damping
current limitation threshold for the target damping current (second
post-limitation target value TVa2) and the extension/contraction
current limitation threshold for the target extension/contraction
current (third post-limitation target value TVa3). This
configuration is based on a fact that the damping control and the
extension/contraction control are simultaneously performed using
the drive current acquired by adding the target damping current and
the target extension/contraction current.
[0189] The damping current limitation threshold (second
post-limitation target value TVa2) and the extension/contraction
current limitation threshold (third post-limitation target value
TVa3) are individually determined, for example, according to the
priority on the riding comfort and steering stability of the
vehicle 10. This means, for example, that the damping control
involving mainly the steering stability is performed with priority
over the extension/contraction control mainly involving the riding
comfort of the vehicle 10.
[0190] The electrically powered suspension system 11 according to
the first aspect performs the damping control mainly involving the
steering stability with priority over the extension/contraction
control mainly involving the riding comfort of the vehicle 10 when
determining that the electric motor 31 is in the excessive heat
generation state, and therefore is able to achieve the accurate
vibration control of the vehicle 10 without disturbing the behavior
of the vehicle 10 and without impairing the riding comfort of the
vehicle 10 as much as possible even when the electric motor 31
provided in the electromagnetic actuator 13 is in the excessive
heat generation state.
[0191] Further, the electrically powered suspension system 11
according to the second aspect is the electrically powered
suspension system 11 according to the first aspect, wherein the
extension/contraction current limitation threshold (the third
post-limitation target value TVa3) is set to a value smaller than a
damping current limitation threshold (the second post-limitation
target value TVa2).
[0192] As described above, the energization time for the
extension/contraction control of the vibration wave per unit cycle
tends to be longer than the energization time for the damping
control of the vibration wave per unit cycle. In other words, the
amount of work (heat quantity) for the extension/contraction
control of the vibration wave per unit cycle tends to be larger
than the amount of work (heat quantity) for the damping control of
the vibration wave per unit cycle.
[0193] The electrically powered suspension system 11 according to
the second aspect is able to give priority to performing the
current limitation of the extension/contraction control that
involves the riding comfort of the vehicle 10 and tends to generate
a larger amount of heat than the damping control over the current
limitation of the damping control, and at the same time, to make
the current limitation of the damping control (involving
suppression of the unsprung vibration) difficult to start and
thereby can achieve the accurate vibration control of the vehicle
10 without disturbing a behavior of the vehicle 10 and without
impairing the riding comfort of the vehicle 10 as much as possible
even if the electric motor 31 provided in the electromagnetic
actuator 13 is in the excessive heat generation state.
[0194] The electrically powered suspension system 11 according to
the third aspect is the electrically powered suspension system 11
according to the first or second aspects, wherein the damping
current limitation threshold (the second post-limitation target
value TVa2) and the extension/contraction current limitation
threshold (the third post-limitation target values TVa3) each is
set on a basis of the current correlation value correlating with
the drive current of the electric motor 31.
[0195] Here, the current correlation value correlated with the
drive current of the electric motor 31 is a property that naturally
includes the drive current itself of the electric motor 31, and
further comprehensively includes current correlation values that
can give an accurate estimate about the heat generation state of
the electric motor 31, such as a current correlation value of the
electric motor 31 converted from a temperature around a substrate
of the ECU 15 that performs the drive control of the
electromagnetic actuator 13; and a current correlation value of the
electric motor 31 converted from a temperature around a housing of
the electric motor 31.
[0196] The electrically powered suspension system 11 according to
the third aspect may configure each of the damping current
limitation threshold and the extension/contraction current
limitation threshold on a basis of the current correlation values
correlating with the driving current of the electric motor 31, and
therefore allows to clarify a configuration guideline of the
damping current limitation threshold and the extension/contraction
current limitation threshold to facilitate implementation of the
present invention.
[0197] Further, an electrically powered suspension system 11
according to the fourth aspect is the electrically powered
suspension system 11 including any one of the first to third
aspects, and further includes an information acquisition part 43
that acquires information on a temperature Te of the ECU (drive
control unit) 15, wherein each of the damping current limitation
threshold (the second post-limitation target value TVa2) and the
extension/contraction current limitation threshold (the third
post-limitation target value TVa3) is set on a basis of the
temperature Te of the ECU 15.
[0198] The electrically powered suspension system 11 according to
the fourth aspect may configure each of the damping current
limitation threshold and the extension/contraction current
limitation threshold on a basis of the temperature Te of the ECU
15, and therefore allows to make a clearer configuration guideline
of the damping current limitation threshold and the
extension/contraction current limitation threshold to facilitate
implementation of the present invention more than the electrically
powered suspension system 11 according to the third aspect.
[0199] Further, the electrically powered suspension system 11
according to the fifth aspect is the electrically powered
suspension system 11 according to any one of the first to third
aspects, and further including an information acquisition part 43
that acquires information on the temperature Tm of the electric
motor 31, wherein each of the damping current limitation threshold
(the second post-limitation target value TVa2) and the
extension/contraction current limitation threshold (the third
post-limitation target value TVa3) is configured on a basis of the
temperature Tm of the electric motor 31.
[0200] The electrically powered suspension system 11 according to
the fifth aspect may configure each of the damping current
limitation threshold and the extension/contraction current
limitation threshold on a basis of the temperature Tm of the
electric motor 31, and therefore allows to make a clearer
configuration guideline of the damping current limitation threshold
and the extension/contraction current limitation threshold to
facilitate implementation of the present invention more than the
electrically powered suspension system 11 according to the third
aspect.
[0201] Further, the electrically powered suspension system 11
according to the sixth aspect is the electrically powered
suspension system 11 including any of the first to third aspects,
wherein the damping current limitation threshold (the second
post-limitation target value TVa2) and the extension/contraction
current limitation threshold (the third post-limitation target
value TVa3) are independently configured in consideration of at
least the priority on the riding comfort and the driving stability
of the vehicle 10.
[0202] This means that the damping control mainly relating to the
steering stability is performed with priority over the
extension/contraction control mainly relating to the riding comfort
of the vehicle 10.
[0203] The electrically powered suspension system 11 according to
the sixth aspect performs the damping control mainly involving the
steering stability with priority over the extension/contraction
control mainly involving the riding comfort of the vehicle 10 when
determining that the electric motor 31 is in the excessive heat
generation state, and therefore is able to achieve the accurate
vibration control of the vehicle 10 without disturbing the behavior
of the vehicle 10 and without impairing the riding comfort of the
vehicle 10 as much as possible even when the electric motor 31
provided in the electromagnetic actuator 13 is in the excessive
heat generation state, similarly to the electrically powered
suspension system 11 according to the first aspect.
Other Embodiments
[0204] The embodiment and the plurality of modifications described
above show examples for implementations of the present invention.
Therefore, the technical scope of the present invention should not
be construed to be limited to these embodiment and modifications.
The present invention can be implemented in various embodiments
without departing from the gist or the main scope of the present
invention.
[0205] In addition, the description is given of the embodiment of
the extension/contraction control of the electromagnetic actuator
13 in the electrically powered suspension system 11 according to
the embodiment of the present invention, by exemplifying the
control performed using the skyhook control that suppresses the
vertical vibration of the vehicle body on the basis of the sprung
speed BV, but the present invention is not limited to this
embodiment.
[0206] The present invention may be applied, for example, on a
control for suppressing roll vibration of the vehicle body based on
the roll angular velocity of the vehicle body and a control for
suppressing pitch vibration of the vehicle body based on the pitch
angular velocity of the vehicle body, as another embodiment of the
extension/contraction control of the electromagnetic actuator
13.
[0207] Further, the electrically powered suspension system 11
according to the embodiment is described in the embodiment that
arranges the total of four electromagnetic actuators 13 on both the
front wheels (front right wheel and front left wheel) and the rear
wheels (rear right wheel and rear left wheel). However, the present
invention is not limited to this specific embodiment. For example,
the total of two electromagnetic actuators 13 may be arranged in
either one of the front wheels and the rear wheels.
[0208] Finally, the electrically powered suspension system 11
according to the embodiment is described such that the drive
controller 49 performs independent drive control of each of the
plurality of electromagnetic actuators 13. To be more specific, the
drive controller 49 may perform independent drive control of each
of the electromagnetic actuators 13 respectively provided in the
four wheels for each of the wheels. Further, the drive controller
49 may performs independent drive control of the electromagnetic
actuators 13 respectively provided for the four wheels, separately
for the front wheels and for the rear wheels, or separately for the
right wheels and the left wheels.
* * * * *